BERLIN — A closely watched survey shows that business confidence in Germany, Europe’s biggest economy, has declined slightly although managers’ outlook for the months ahead remains at least slightly optimistic.

The Ifo institute said Monday that its monthly confidence index was down to 101.8 points for June from 102.3 last month. While executives’ outlook for the next six months remained unchanged, their assessment of their current situation darkened slightly.

Economists had forecast a decline to 101.7 amid concerns over trade tensions between the U.S., the European Union, China and others. Hard data on the German economy also have tended to disappoint recently.

Ifo’s survey is based on monthly responses from around 9,000 firms in various sectors of the economy.